Several industries utilize conveyor and process belts for transporting loads from one location to another location or for passing loads through successive processing operations. Various types of conveyor belts are used for this purpose depending on the application, the materials being transported, and the environmental conditions under which the conveyor belt is operating. For example, traditional conveyor belts include layers or plies of fabric carcass material embedded between thermoplastic or rubber layers. On the other hand, monolithic conveyor belts are often used in applications that require light to medium duty conveyor belts, particularly where sanitary conditions are required, such as, for example, in the food industry. Unlike traditional conveyor belts, monolithic conveyor belts are typically formed from a single homogenous material, for example a thermoplastic material, although they may include other composite materials such as reinforcing fibers. Forming the belt from a single thermoplastic material is often desirable because the thermoplastic material is less prone to providing sites for microbiological growth due to contamination from, for example, contact with conveyed food or dairy products. Several other types of conveyor belts are also utilized in various industries and are selected depending on the demands of a particular application.
During installation and repair of conveyor belts, it is often necessary to join together the ends of one or more belts. Various tools and methods have been used to join the conveyor belt ends together. For example, mechanical fasteners are used to mechanically fasten the belts together. Similarly, adhesives are similarly used to adhere the ends of the conveyor belt ends to one another. Other approaches including vulcanized splicing or welding of the belt ends, which includes heating the belt ends to a temperature near or above the melting temperature of at least a component of the belt material and simultaneously or subsequently abutting the belt ends together to allow the material of the belt ends to intermix and harden to join the belt ends together. Other joining techniques, including cold bonding, are also known for joining the belt ends together.
While several methods exist for joining the belt ends to one another, the ends of the belts must typically be prepared in advance of being joined. To this end, the belt ends are typically cut or prepared in a manner that allows the belt ends to abut each other in a manner that will result in the belt ends being aligned when the ends are joined together. In one approach, the belt ends are prepared in corresponding finger-shaped or other corresponding patterns that intermesh with each other so that the belt ends abut or are closely adjacent with both of the belts extending in a generally longitudinal direction so that a square belt is formed. In another approach, the belts are cut across their lateral width to square the belt ends so that they extend orthogonally or at similar angles to the belt edges, so that the ends are relatively straight and parallel with the belts each extending in a longitudinal direction so that the belt ends can be joined together to form a generally linear belt or square belt.
A typical conveyor belt joining process for cutting and joining the belt ends generally includes first cutting the conveyor belt ends so that the belt ends can be positioned end-to-end with the belts being generally square to one another. The belts are subsequently joined together by one of the processes described above, either by hand or using a separate tool.
Commonly owned U.S. patent application Ser. No. 12/888,411, published as US 2011/0067801, to van 't Schip, incorporated in its entirety by reference herein, describes a conveyor belt welding apparatus for welding together the ends of one or more monolithic conveyor belts, and is hereby incorporated by reference as if it were reproduced in its entirety herein. In the '801 publication, the welding apparatus includes a pair of spaced grooved platens for supporting the conveyor belt ends and a heating device that is movable to a position between the belt ends for heating and melting the material thereof. After moving the heating device to a stowed position, the belt ends are then moved toward each other to intermix the belt material of the two ends which then cools to join the ends together. The application describes that the welding apparatus may be used for positive drive conveyor belts, which include depending projections such as laterally extending fins or ribs that depend from the bottom of the belt and interengage with and are driven by mating recesses in a drive pulley of the conveyor belt system. Alternatively, rows of depending lugs may be utilized instead of a continuous fin or rib. Herein, the term drive bar will be utilized and will be understood to include both a continuously extending fin or rib as well as a row of lugs. The '801 Publication describes a separate cutting template used to form square cuts across a positive drive belt and which is sized to maintain the distance or “pitch” between adjacent drive bars after the belt is joined together. The cutting template is placed near the belt end and includes grooves that receive one or more drive bars of the belt end to be cut. The cutting template includes a cutting guide edge that is spaced a predetermined distance from an adjacent groove so that a predetermined pitch may be maintained between adjacent drive bars of the belt. With the belt placed on a flat surface so that the drive bars project upwardly, the cutting template is place on the belt end with the drive bars received in the grooves and a utility knife is manually drawn along the template cutting guide edge to cut or score the belt a predetermined distance from the adjacent drive bar.
Another conveyor belt welding device provided by Intralox includes a clamping fixture having a pair of grooved decks with a drive mechanism for shifting the decks, and the belt ends supported thereon toward and away from each other. A separate elongate contact heating wand is provided to be manually inserted between the belt ends by an operator. The operator then drives the decks toward one another to engage the belt ends against the heating wand to melt the belt ends. The wand is removed and the belt ends are shifted more closely together to clash the belt ends together and form a weld therebetween.
For preparing the belt ends, the belt welding device includes a separate cutting guide with grooves for receiving the drive bars of a positive drive belt. The belt may be prepared using the clamping fixture with the belt supported on the decks facing up or down with the belt drive bars received in the grooves of either the cutting guide or the deck. If the drive bars face up with the belt end supported on the decks, the operator needs to visually align the drive bars with the grooves in the underlying decks. Otherwise, the belt end has its drive bars received in the grooves of the decks. The belt end to be cut is pulled over a first one of the decks, over the gap between the grooved decks, and onto the second deck until at least an inch of material extends past the far edge of the second deck. The cutting guide is connected to the second deck, clamped down on the belt end portion and an operator manually draws a utility knife along the straight guide edge of the cutting guide to cut the belt end. The opposite belt end is prepared in the same manner. After the belt ends are cut, the belts ends are moved to their respective heating and joining grooved deck and their drive bars are inserted into grooves of the grooved decks where they will be heated and joined as described previously.
While the cutting template and cutting guides, are useful for forming relatively square belt ends for joining together conveyor belt ends, both are time consuming and require additional pieces of equipment that belt repair personnel must transport to the location where a belt needs to be repaired or installed. One of the cutting guides has to be individually mounted to the device for cutting, and then removed from the device after the first belt end has been cut to allow for the next belt end to be cut, with another cutting guide then mounted to the device for cutting the second belt end. In addition, the quality of the cut belt end will vary because it depends on the operator holding the knife in a vertical position and closely following the cutting guide along the cutting edge. If an operator holds the cutting knife at an incline from the vertical position or accidentally moves the knife away from the cutting edge, the belt ends may not be evenly squared across their lateral ends resulting in uneven heating and potentially gaps being formed between the resulting welded belt ends. Unsquare belt ends may also result in the belts not being properly aligned when they are joined.
Further, because the grooves for both the cutting template and cutting guide and the belt support platens or grooved decks in the above systems are machined with tolerances, cutting with the drive bars in the grooves of the cutting template or cutting guides and subsequently heating and welding the belts together with the belts on the platens or decks and the drive bars positioned in platen or deck grooves can lead to tolerance stackup problems. Similarly, when the belt is cut with the drive bars facing down and received in a different groove on the grooved deck than the groove the drive bar will be in during heating and joining operations as in the Intralox device, tolerances in the machining of the different grooves of the groove deck can result in tolerance stackup. The tolerance stackup can result in inaccurate positioning of the cut end portions relative to the heating element so that the belt ends do not receive the correct amount of heat, and so that the amount of clash between the belt ends varies from a predetermined amount of clash, forming a weaker weld. Problems associated with lack of uniform heating include potential buckling of the belt in the splice area or having an undesirable increase in the pitch where an insufficient amount of belt material is melted, or none at all so that there is little or no intermixing of belt material from both of the belt ends to be joined in the area that is insufficiently heated. Alternatively, too much heat can result in burning or bubbling of the belt material which also can create a non-uniform splice.
Problems associated with small variations in the cut belt ends and tolerance stackup may be magnified in these systems, because during welding, for example with the apparatus described by van 't Schip, the heated belt ends may only be clashed together by a very small amount, for example 1 mm, so that small variations in the amount of belt material at the cut belt ends may result in portions of the lateral widths of the belts being clashed together by too little or too great an extent. This can have an adverse effect on maintaining a precise pitch between drive bars across the splice. In addition, in the van 't Schip apparatus, the belts are positioned at a predetermined heating position where the belt ends are positioned a predetermined distance from a non-contact heating element where the amount of radiant heat the belts receive is a function of the distance of the belts from the heating element, so variations in the cut along the belt lateral width may result in uneven heating of the belt ends.
U.S. Pat. No. 5,020,209 to Fullard et al., on the other hand, discloses a belt lacing machine having a cutter blade apparatus for cutting the end of a belt and for clinching belt fasteners to the cut belt end. The belt is initially positioned and clamped in a cutting section of the machine. A carriage carries a blade that extends up through a longitudinal slot in the belt mounting surface and a drive handle is rotated to drive the carriage and blade to cut transversely across the belt end. The machine has mechanical, hook or C-shaped belt fasteners, and the cut belt end is then manually advanced further into the lacer machine and the fasteners are shifted to receive the cut belt end in their open jaws. Then the belt end is clamped, and the lacer rollers are driven along the belt end to clinch open legs of the fasteners closed and into the belt end. Another belt end must be prepared separately in the same manner. Once fasteners are separately secured to both belt ends, an operator removes the belt ends from the cutting and clinching machine for joining the belt ends together. For joining the belt ends, the operator must align the belt ends and interlace the belt fasteners of the two belt ends together. While maintaining the fasteners in an interlaced condition, the operator must carefully thread a splice pin through aligned openings of the fasteners to mechanically splice the belt ends together. While this process is useful for providing a straight cut and joining belt ends together, the Fullard machine is for installing a mechanical splice and requires a multiple step approach that includes rearranging and/or moving the belt ends several times during the procedure. The belt cutting area of the machine is different from where the fasteners are clinched onto the belt ends, which requires an increase in the over all size of the machine, and the belt ends are joined together outside the machine. In addition, an operator must premark the belt for cutting and then eyeball the belt to ensure that it is properly aligned in the machine so that the cut is made along the premark straight across the lateral width of the belt ends. It also requires the operator to separately prepare the belt ends in the machine and join them together after being removed from the machine, requiring additional time to join the belt ends together.